Process of plating aluminum



Patented Feb- 10, 1931 LOUIS seminars; or PITTSBURGH, PENNSYLVANIA rnocnss or rLA'rING ALUMINUM- I No Drawing.

'l'hisinvention relates to improvements in ii-(messes of plating aluminum and an object thereof is to produce a process of plating that is commercially practicable and that can be applied to the,plating of aluminum with brass, copper, silver, gold, nickel, bronze. etc.

The process herein set forth is applicable to the plating ofwhat is known as commerciallypure aluminum and to an alumiw num base alloy and both are contemplated by the term aluminum as used in this specification and claim. The invention has to do both with plated aluminum articles and with a process for plating aluminum l articles and the term articles is used to designate both. partly finished ware and finished ware.

In carrying out my process, I first passivify the surface of the article to be plated by dipping the same in a solution of nitric acid. This solution, I find, can range in strength from 2% to the concentrated form. A concentrated solution, however, is preferred.

As a second step of my process, I electroz'f plate the article with an alloy of nickel and iron in which the iron content of the alloy is just great enough to cause the plating to firmly adhere to the, aluminum. Iron is positive -to nickel and nearer in the series to aluminum than is nickel, copper or silver. v

For obtaining the iron nickel alloy deposit,

I preferably use a solution of about 10 to 12 oz.-of double nickel salts (that isnickel sulphate and ammonia) and from 1 to 2 oz. of

iron sulphate and ammonia with one gallon of water. To this I add sodium sulphate as a conducting salt.

Such a solution will readily plate on any kind of aluminum Ware if the surface of the 4 wear is first passivified as described and unless the surface is passivified, the alloy plating will peel off if the ware is bent or dented.

Applicationfiled m 29, 1926-. Serial No. 112,688.

makes a soft nickel and iron deposit which is desirable on the aluminum base, since the aluminum itself is soft.

The nickel iron plating in itself may be useful for some purposes, but I prefer to merely give a light plating of this alloy fol-.

lowed by a heavier coating of the final plating metal. After the light coating, the article should be rinsed before the second coat ing is applied.

For plating with nickel, I prefer to follow the first coating which I termthe ground coat, with a bright nickel coating made in any of the Well known ways. I find that I can plate various metals such as silver, gold, brass, copper, bronze or nickel on top of the ground coat. The coatings containing cop per, suchas brass and bronze can be colored in any desired Way now well known. If a stainless surface is desired, chromium or an alloy containing'chromium can be plated on top of the ground coat.

Having thus described my invention, what I claim is i The process of plating articles of alumi- 7 num, comprising passivifying the surface of the aluminum article, plating the passivified surface with an alloy of nickel and iron by the electrodeposition process in a bath containing'nickel sulphate, iron sulphate, and a s0 conducting salt and then electroplating the nickel iron coating with some finishing metal.-

In testimony whereof, I have hereunto subscribed my name this 26th day of May, 1926.

' LOUIS SCHULTE. s5

A single salt solution composed of sulphate of nickel and sulphate of iron or a 4 combination of these two with a conducting salt may be used. Such salts are well known in the electroplating art and consist of chloride of ammonium, chloride of sodium and sulphate of magnesium or sodium. I prefer,

5 however, "to use sodium sulphate, since this 

